Add an option to use LLD to link the compiler on Windows platforms

1 files changed, 23 insertions, 3 deletions

diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index d9c894aa9c6..008af975c33 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -694,7 +694,7 @@ impl<'a> Builder<'a> {
         cmd.env_remove("MAKEFLAGS");
         cmd.env_remove("MFLAGS");
 
-        if let Some(linker) = self.linker(compiler.host) {
+        if let Some(linker) = self.linker(compiler.host, true) {
             cmd.env("RUSTC_TARGET_LINKER", linker);
         }
         cmd
@@ -949,10 +949,30 @@ impl<'a> Builder<'a> {
             }
         }
 
-        if let Some(host_linker) = self.linker(compiler.host) {
+        // FIXME: Don't use LLD if we're compiling libstd, since it fails to link it.
+        let can_use_lld = mode != Mode::Std;
+
+        // FIXME: The beta compiler doesn't pick the `lld-link` flavor for `*-pc-windows-msvc`
+        // Remove `RUSTC_HOST_LINKER_FLAVOR` when this is fixed
+        let lld_linker_flavor = |linker: &Path, target: Interned<String>| {
+            compiler.stage == 0
+                && linker.file_name() == Some(OsStr::new("rust-lld"))
+                && target.contains("pc-windows-msvc")
+        };
+
+        if let Some(host_linker) = self.linker(compiler.host, can_use_lld) {
+            if lld_linker_flavor(host_linker, compiler.host) {
+                cargo.env("RUSTC_HOST_LINKER_FLAVOR", "lld-link");
+            }
+
             cargo.env("RUSTC_HOST_LINKER", host_linker);
         }
-        if let Some(target_linker) = self.linker(target) {
+
+        if let Some(target_linker) = self.linker(target, can_use_lld) {
+            if lld_linker_flavor(target_linker, target) {
+                rustflags.arg("-Clinker-flavor=lld-link");
+            }
+
             let target = crate::envify(&target);
             cargo.env(&format!("CARGO_TARGET_{}_LINKER", target), target_linker);
         }